1. Field of the Invention
The present invention relates generally to a photographing apparatus and a photographing method thereof, and more particularly, to a photographing apparatus and method using a focal plane shutter.
2. Description of the Related Art
The shutter of a camera may be generally classified into a lens shutter and a focal plane shutter. The lens shutter is located in the proximity of a lens, whereas the focal plane shutter is located in the proximity of a focal surface.
The focal plane shutter is classified into a horizontal shutter and a vertical shutter, according to moving directions of front and rear curtains. The vertical shutter enjoys wide use due to efficient performance.
The focal plane shutter is located in front of an image sensor of a camera and passes or blocks light which penetrates a lens by opening or closing the front and rear curtains in front of the image sensor of the camera according to an operation state of the camera. When a user starts photographing, the front curtain moves as illustrated in FIG. 1A, thereby starting light exposure of an image sensor, which light exposure concludes as the rear curtain moves after a time elapses according to a shutter speed determined by the camera.
The focal plane shutter has several disadvantages. First, a shutter release lag increases when a live-view is used. Recently, an Electronic View Finder (EVF) or a live-view image photographed by an image sensor of a rear Liquid Crystal Display (LCD) has been more commonly used instead of an Optical View Finder (OVF). For this, a focal plane shutter maintains an open state in which a front curtain is down and a rear curtain is up. In this state, when a user starts photographing, a charging operation in which the front curtain, which has been down, is raised to an upper part of the shutter is required. That is, as a shutter operation sequence increases to provide a live-view image, a shutter release lag also increases.
Second, image quality may deteriorate due to shutter shock. In a focal plane shutter, the movement of a front curtain is completed during the light exposure of an image sensor as illustrated in FIG. 1A. As the movement of the front curtain is completed, mechanical vibration occurs, shaking the image sensor and thereby causing to deterioration of image quality.
In order to resolve the above disadvantages, an electronic shutter that serves as a front curtain of a focal plane shutter by sequentially processing a reset signal of an image sensor by pixel line is widely used as illustrated in FIG. 1B.
The electronic shutter controls a light exposure time of an image senor according to transmission of an electronic signal of the image sensor and operation of a mechanical rear curtain, so a timing of the electronic signal of the image sensor should be closely interlocked with a moving characteristic of the mechanical rear curtain. Conventionally, a detection unit is provided to add a photographing sequence for observing or detecting a moving characteristic of a mechanical rear curtain so that an electronic signal of an image sensor and an operation time of a mechanical rear curtain may be adjusted.
However, according to the conventional method, the detection unit should be provided on a focal plane shutter, which increases the size and price of the focal plane shutter. If a photo interrupt is used to detect a moving characteristic of a mechanical rear curtain, light entering into a lens should be shielded, which may cause technical difficulty.
In addition, if a moving characteristic of a mechanical rear curtain is detected using an image formed on an image sensor without using a detection unit, further image photographing is required to detect the moving characteristic of the mechanical rear curtain, causing inconvenience to a user.